Applicant has previously proposed a method of producing aerated soap which does not invite defects such as chipping on removal from the mold thereby to provide soap bars with an excellent appearance (see JP-A-2002-121599). The method comprises cooling and solidifying molten soap poured into a mold until the soap surface temperature falls to 5° to 30° C., elevating the temperature of the solidified soap until the surface temperature becomes higher by 2° to 15° C. than the surface temperature at the end of the cooling, and removing the soap bar from the mold. The mold used in the method has a surface roughness Ra of 0.1 to 30 μm on its inner side.
The method allows for successful removal from the mold even though the soap is more liable to chipping than ordinary soap because of air bubbles. At mold opening, however, the solidified soap bar tends to fall without being secured to a split of the mold. The soap bar very easily breaks up if dropped, which results in contamination of the production equipment. A soap bar should therefore be held in a split without fail. Apart from that issue, which split a soap bar holds to when the mold is opened tends to differ from cycle to cycle. This means that the step of removal from the mold with a handling unit tends to be complicated, which can reduce the productivity.
It has been proposed to apply a coating providing different releasability to the recess of a split of a mold so that adhesion of soap may differ between splits (see JP-T-2001-525881). However, the coating gradually comes off with the number of shots, eventually resulting in no difference in adhesion. It is therefore necessary to apply the coating to the split periodically, which makes the molding operation complicated and increases the production cost.